I use wool blankets as 'batting' in wool quilts all the time, both tied and quilted. They work just fine and are no heavier than three wool blankets on a bed...something found often in this neck of the woods. Sleeping heat is well below daytime heat for many reasons.
I would NOT use the envelope method (aka 'birthing') however. Blankets do not have the same stretch as batting so you may run into problems after turning. I just do the same as any other quilt with mine.